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008 181022s2018 xx sbm 000 0 eng d
020 9780438241855
035 (MiAaPQ)AAI10810508
035 (MiAaPQ)udel:13321
040 MiAaPQ|beng|cMiAaPQ|dNTU
100 1 Caldwell, Andrew D
245 10 Coiling Direction of the Planktic Foraminifer Globorotalia
truncatulinoides as a Proxy for Reconstructing Upper Ocean
Hydrography in the North Atlantic during the Mid-
pleistocene Climate Transition
264 0 |c2018
300 1 online resource (64 pages)
336 text|btxt|2rdacontent
337 computer|bc|2rdamedia
338 online resource|bcr|2rdacarrier
500 Source: Masters Abstracts International, Volume: 58-01
500 Adviser: Katharina Billups
502 Thesis (M.S.)--University of Delaware, 2018
504 Includes bibliographical references
520 This study uses the coiling direction of the planktic
foraminifer Globorotalia truncatulinoides as a proxy for
reconstructing past changes in upper ocean hydrography in
the northwestern subtropical Atlantic Ocean during the mid
-Pleistocene climate transition (̃0.4 -- 1.2 Ma). The mid-
Pleistocene transition is a time interval of interest
because it encompasses the evolution of glacial-
interglacial cycles from less severe, 41 kyr-paced
glaciations to more severe, 100 kyr-paced glaciations,
without any observable changes in corresponding orbital
forcing. I hypothesize that the establishment and
persistence of the more extreme glaciations characteristic
of the current 100 kyr world was associated with changes
in the hydrography of the subtropical North Atlantic and
the related poleward heat transport, evident in the
downcore coiling ratio of G. truncatulinoides. The Gulf
Stream and surrounding North Atlantic current system
transport a substantial amount of heat from the equator to
the poles, and therefore have a significant climatic
impact on large temporal and spatial scales. Here I test
whether or not changes in subtropical gyre dynamics,
particularly the relative strength and position of the
Gulf Stream and subtropical gyre, played a role in
contributing to the onset of the 100 kyr cycle. To do this,
I will construct a record of downcore variations in the
coiling direction of G. truncatulinoides spanning the mid
-Pleistocene transition. Studies have shown that there are
spatial and temporal differences in the coiling direction
of G. truncatulinoides through time as a result of
changes in oceanic conditions; for example, sediments
dominated by left coiling specimens characterize
interglacial periods and deeper permanent thermoclines,
while sediments dominated by right coiling specimens
characterize glacial periods and shallower permanent
thermoclines. Deeper permanent thermoclines are
characteristic of interglacial periods due to enhanced
flow of the subtropical gyre and Gulf Stream, and
therefore greater poleward heat transport; these
environmental conditions favor the left coiling variety of
G. truncatulinoides. Conversely, shallow permanent
thermoclines are characteristic of glacial periods due to
reduced flow of the subtropical gyre and Gulf Stream,
favoring the right coiling variety. There have been
studies exploring the hydrography of the subtropical North
Atlantic across parts of the mid-Pleistocene transition,
but not necessarily across the entire interval. This study
will provide valuable insight into the relative position
of the Gulf Stream and the North Atlantic subtropical gyre
across the mid-Pleistocene transition, exploring the
implication of these features on oceanic heat transport
533 Electronic reproduction.|bAnn Arbor, Mich. :|cProQuest,
|d2018
538 Mode of access: World Wide Web
650 4 Paleoclimate science
655 7 Electronic books.|2local
690 0653
710 2 ProQuest Information and Learning Co
710 2 University of Delaware.|bMarine Studies
773 0 |tMasters Abstracts International|g58-01(E)
856 40 |uhttps://pqdd.sinica.edu.tw/twdaoapp/servlet/
advanced?query=10810508|zclick for full text (PQDT)
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